Recent R&D and roadmap toward Space Based Solar Power in Japan Abstract : We carry out Research and Developments toward Space Based Solar Power (SBSP) from 2009 in Japan. It is mainly development of novel microwave power transfer system with light weight and high efficiency phased array system at 5.8GHz. In 2023, we are in phase 3 and developing higher efficiency high power amplifier with GaN device and sandwich module transmitter. We will carry out long distance (>1km) wireless power transfer demonstration. It is pre-experiment for small satellite experiment as phase 4 of the Japanese project, which will be carried out in 2025. In this talk, I introduce the recent Japanese R&D project and hopeful roadmap toward the SBSP.